Phosphate ester formation

SOME GENERAL METHODS FOR PHOSPHATE ESTER FORMATION REMOVAL OF PROTECTIVE GROUPS FROM PHOSPHORUS... 

Cleavage is achieved with refluxing NaOH (15 min), but some deamination occurs with deoxyriboadenosine-5 -phosphate. The ester is formed using the DCC protocol for phosphate ester formation. 

Figure 6.22. Mechanism of phosphate ester formation by phosphorylation of cellulose (Jagtoyen and Derbyshire, 1998).

These reactions are catalyzed by kinases, some of viiich have already been discussed in this chapter. The reaction may be virtually irreversible as in phosphate ester formation. Here the phosphate acceptor may be a hydroi l group of a carbohydrate (glucose, ycerol, fructose, nucleotides, etc.), (Moline, or pantetheine. The terminal phosphate may also be transferred to an acceptor without loss of high chemical potential, such as to nucleoside mono- or diphosphate or to a nitro n atom. These reactions are freely reversible. Nucleotide diphosphate may also donate its terminal phosphate as in the nucleotide monophosphate kinase reaction. 

In keeping with its biogenetic origin m three molecules of acetic acid mevalonic acid has six carbon atoms The conversion of mevalonate to isopentenyl pyrophosphate involves loss of the extra carbon as carbon dioxide First the alcohol hydroxyl groups of mevalonate are converted to phosphate ester functions—they are enzymatically phosphorylated with introduction of a simple phosphate at the tertiary site and a pyrophosphate at the primary site Decarboxylation m concert with loss of the terti ary phosphate introduces a carbon-carbon double bond and gives isopentenyl pyrophos phate the fundamental building block for formation of isoprenoid natural products... 

Metabolic Functions. The formation of phosphate esters is the essential initial process in carbohydrate metaboHsm (see Carbohydrates). The glycolytic, ie, anaerobic or Embden-Meyerhof pathway comprises a series of nine such esters. The phosphogluconate pathway, starting with glucose, comprises a succession of 12 phosphate esters. 

For extraction of uranium from sulfate leach Hquors, alkyl phosphoric acids, alkyl phosphates, and secondary and tertiary alkyl amines are used in an inert diluent such as kerosene. The formation of a third phase is suppressed by addition of modifiers such as long-chain alcohols or neutral phosphate esters. Such compounds also increase the solubihty of the amine salt in the diluent and improve phase separation. 

Thiamine forms the expected derivatives of the thia zole alcohol function, such as carboxyUc and phosphate esters. Eew reactions at the pyrimidine 4-amino function have been reported. Most of the usual conditions used for formation of amides, for example, lead to destmction of the thiazolium ring. 

Acid chlorides are used for the quantitative deterrnination of hydroxyl groups and for acylation of sugars. Industrial appHcations include the formation of the alkyl or aryl carbonates from phosgene (see Carbonic and chloroformic esters) and phosphate esters such as triethyl, triphenyl, tricresyl, and tritolyl phosphates from phosphoms oxychloride. 

DNA is not susceptible to alkaline hydrolysis. On the other hand, RNA is alkali labile and is readily hydrolyzed by dilute sodium hydroxide. Cleavage is random in RNA, and the ultimate products are a mixture of nucleoside 2 - and 3 -monophosphates. These products provide a clue to the reaction mechanism (Figure 11.29). Abstraction of the 2 -OH hydrogen by hydroxyl anion leaves a 2 -0 that carries out a nucleophilic attack on the phosphorus atom of the phosphate moiety, resulting in cleavage of the 5 -phosphodiester bond and formation of a cyclic 2, 3 -phosphate. This cyclic 2, 3 -phosphodiester is unstable and decomposes randomly to either a 2 - or 3 -phosphate ester. DNA has no 2 -OH therefore DNA is alkali stable. 

One of the most widely used methods for the formation of phosphate esters involves the conversion of a P-N bond of a phosphorus(III) compound to a P-O bond by ROH, catalyzed by l//-tetrazole, followed by oxidation to the phosphorus(V) derivative ... 

Formation of emulsions of the oil-in-water or water-in-oil type depends mainly on the hydrophilic-lipophilic balance (HLB) of the emulsifier. Phosphate esters with their various molecular structures can be adjusted to nearly every HLB value desired. Therefore they are able to meet nearly all of demands in this field. 

Emulsions are frequently used in the formulation of herbicides. Such emulsions have to form stable concentrates. They will be diluted with water before applying on plants. In this form too the surfactants used have to support the formation of fine droplets at the nozzles and provide a sufficient wetting of leaves. Surfactants have to be used which will not interfere with water hardness. Therefore phosphate esters and phosphonic esters are often applied. 

For formation of anticorrosive and adhesion-improving protective layers on metals the cleaned surface is treated with aqueous acidic solution containing molybdate, chromium fluoride, phosphate, acetate, and Zn ions. As dispersant a mixture of 60% alkali salt of a phosphate ester, 20% alkylpolyglucoside, and 20% fatty alcohol ethoxylate was applied. This method passivates the metal surface by formation of an anticorrosive and protective layer that improves adhesion of subsequent coatings. 

Solubilizing activity are also used in enhanced oil recovery. Tar and extremely viscous hydrocarbons are recovered by the injection of an aqueous solution of an anionic orthophosphate ester surfactant into a petroleum formation, retaining the surfactant in the formation for about 24 h, and displacing the solubilized hydrocarbons toward a recovery well. The surfactant forms an oil microemulsion with the hydrocarbons in the formation. An anionic monoorthophosphate ester surfactant which is a free acid of an organic phosphate ester was dissolved in water. The input of surfactant solution was 2-25% of the pore volume of the formation [250]. To produce a concentrate for the manufacture... 

J. P. Guthrie, Hydration and Dehydration of Phosphoric Acid Derivatives Free Energies of Formation of the Pentacoordinate Intermediates for Phosphate Ester Hydrolysis and of Monomeric Metaphosphate, J. Am. Chem. Soc. 1977, 99, 3391. 

SCHEME 10.2 Common pathways of QM formation in biological systems, (a) Stepwise two-electron oxidation by cytochrome P450 or a peroxidase, (b) Enzymatic oxidation of a catechol followed by spontaneous isomerization of the resulting n-quinone. (c) Enzymatic hydrolysis of a phosphate ester followed by base-catalyzed elimination of a leaving group from the benzylic position. 

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